Conventional integrated circuits, with a serial data port for loading data into an adequate register, require an address bit stream in addition to a data bit stream to steer the data to the adequate register among several registers. For example, in order to randomly access one of five registers, three address bits are required. If data to be loaded has an eight-bit length, a total of a least 11 bits is needed in the bit stream. This means that it takes an undesirably long time to load data into registers in the prior art integrated circuits. Besides the length of the 11-bit stream is very awkward for 8-bit and 16-bit microprocessors to handle. In order to transmit the 11-bit data, the use of a 16-bit (two bytes) data stream may be required, especially with serial peripheral interfaces (SPI). In this case, each 16-bit data stream includes a 5-bit useless stream (overhead), and that makes it unnecessarily harder to write a program. And, of course, it takes much more time to load data. In the case of loading 16-bit length data into one-of-five registers, a total of at least 19-bits is needed in the bit stream. Therefore, the use of a long 24-bit (three bytes) data stream may be required. Such long data streams may require too much time to transfer data in many applications.